Encapsulated particles that include layers, such as a sulfur layer, and core particles are known in the art. Thickness and external integrity of the sulfur layer limits a rate at which the core particle is released, e.g. dissolves. Prior art encapsulated particles tend to require a large amount of sulfur, e.g. greater than 15% by weight of sulfur based on the total weight of the encapsulated particle, thereby reducing the overall amount of the core particle present in the encapsulated particle. Additionally, a layer consisting of sulfur tends to exhibit brittleness and is subject to breakage during handling. When the sulfur layer breaks or cracks, a portion of the core particle releases quickly and the remainder of the core particle is left partially exposed to water and other liquids which may rapidly dissolve the core particle therefore preventing a controlled release. The rapid dissolution of the core particle is typically undesirable because at least one purpose of encapsulating the core particle is to achieve a controlled release of the core particle over time.
Other prior art encapsulated particles include polyurethane layers as opposed to sulfur layers. However, these encapsulated particles tend to exhibit surface defects and issues with inconsistent external integrity such as partial encapsulation of the core particle by the polyurethane layer, inconsistent thickness of the polyurethane layer, and pits and depressions in the polyurethane layer. Similar to that which is described above, when polyurethane layers with surface defects are disposed about core particles, a portion of the core particle may be left partially exposed or a thin section of the polyurethane layer inconsistent in thickness with the rest of the polyurethane layer may result in water and other liquids rapidly permeating the polyurethane layer. Either scenario described above generally results in rapid dissolution of the core particle, therefore preventing controlled release of the core particle, which is typically undesirable.
Additionally, some encapsulated particles including polyurethane layers agglomerate during the encapsulation process causing a decreased yield of encapsulated particles. Agglomeration typically occurs during encapsulation of the core particles. Agglomeration of the core particles during the encapsulation process tends to reduce encapsulation efficiency, impede complete encapsulation of the core particle by the polyurethane layer, restrict the formation of the polyurethane layer having consistent thickness, increase the amount of the polyurethane layer required relative to the amount of core particles needed to encapsulate the core particle, decrease a yield of encapsulated particles, and cause pits and depressions in the polyurethane layer of the yield of encapsulated particles. Accordingly, there remains a need to develop an improved encapsulated particle and method of encapsulating core particles.